Field of the Invention
The invention relates in general to a display side polarizer for a liquid crystal display (LCD), which can increase LCD's color gamut and optical efficiency such as contrast, color saturation and color accuracy at wide viewing angles.
Description of the Related Art
Displays with high contrast, no gray-scale inversion, no color shift or slight color shift, high brightness, wide color gamut, high color saturation, fast response speed and wide viewing angle are current market trends. Referring to FIG. 1, it shows a cross-sectional view of a conventional liquid crystal display 1. The conventional liquid crystal display 1 includes a liquid crystal module 2 and a backlight module 3. Because the liquid crystal display is a non-self-luminous display, the liquid crystal module 2 needs to be provided with a light source by the backlight module 3 to display an image. Therefore, when the light is vertically and obliquely incident into the liquid crystal layer 23, since the liquid crystal molecules 23a have different symmetry at different viewing angles, the projection components perceived by the vertical incident light L and the oblique incident light L′ passing through the liquid crystal molecules 23a are inconsistent, and it is easy to see the phenomenon of color washout or gray-scale inversion when viewing from the side view, resulting in low contrast or abnormal color performance of the image. Therefore, the image quality does not perform as well as a self-luminous display such as an organic light emitting diode (OLED).
Currently, several methods have been proposed to improve the above shortcomings. For example, a wide viewing angle film (not shown) is disposed on the display side polarizer 21 and the backlight side polarizer 22 of the conventional liquid crystal display 1 to equalize the images between the central viewing angles and the wide viewing angles; a diffusion film or a diffraction film (not shown) is attached on the surface of the display side polarizer 21 to increase the light intensity and contrast at wide viewing angles; quantum dot material is added to the diffusion plate 33 of the backlight module 3; or the quantum dot material is directly used to fabricate the color filter 24 of the liquid crystal module 2 to increase the color saturation and color gamut of the images.
However, the wide viewing angle film for the liquid crystal display is expensive. The diffusion film disposed on the surface of the display side polarizer 21 is difficult to accurately control the direction of the light emitted from different angles of the display, and when the content of the particles in the diffusion film is insufficient, the degree of light scattering cannot be sufficient to transfer the light to larger viewing angles to obtain a non-color shift image at the side viewing angle, and when the content of the particles in the diffusing film is too much, the degree of scattering is too strong and easily appears whitening image to affect the image saturation and contrast. Meanwhile, it is difficult for the diffraction film to synchronously control the light paths of the various viewing angles in different dimensions by the general diffraction structure layer. Adding the quantum dot material to the diffusion plate 33 or the color filter 24 allows the light emitted from the backlight 31 to excite the quantum dots to generate a light with narrow full width at half maximum (FWHM) wavelength to form a wide color gamut image, but the liquid crystal display is still not self-illuminating, and the light emitted from the backlight 31 is uniformly dispersed to each area of the conventional liquid crystal display 1 by the light guide plate 32 and the diffusion particles 33a in the diffusion plate 33, so that the emitted light from the backlight 31 finally has a portion of the normal incident light L and a portion of the oblique incident light L′, and therefore, the side view image is still affected by the liquid crystal molecules 23a and appears color shift or gray-scale inversion. In addition, the color filter 24 needs to have a certain content of the quantum dot material to obtain sufficient color saturation, but the liquid crystal module 2 at least comprises the electrode layer 25, the liquid crystal layer 23, and the color filter 24 disposed between the display side polarizer 21 and the backlight side polarizer 22, and if the content is too large, thereby the polarization degree of light passing through the backlight side polarizer 22 is depolarized by scattering, and the light intensity passing through the display side polarizer 21 is decreased.
Therefore, the present invention is to provide a display side polarizer integrated with quantum dots and diffraction structure layer for increasing color gamut of the liquid crystal display and reducing color washout and gray-scale inversion at wide viewing angles of the liquid crystal display, and increasing the backlight efficiency of the liquid crystal display.